Help - Engine idle rough and revs not smooth

[AJ]

probly wouldn't notice the power drop in an NA6 anyway

/me runs away

[NMX516]

Quite possibly Fatty...

AJ, ever the shite stirrer

[Philip Lee]

thanks guys for your suggestion.

the AFM was installed the correct way (ie. the black bit up).

replaced with another AFM and ECU, still the same.

reconnected the AFC which makes the problem worse.....

i'm completely lost.......

will get professional help.

[ampz]

I'm surious to see what the problem would be.

From the looks of the diagram the only way it would modify the fuel signal would be to modify the AFM signal (ie there doesn'e seem to be enough info that it inersects the PW of your injector banks).

I would hazard a guess that maybe (depending on where the cuts to your harness where made) there has been a wire either crossed or the ground is somehow not enough of a short circuit now.

A vacuum leak (to answer your earlier post) can be any vacuum hose loose or unplugged causing erratic idle.

I hope you didn't fry your ignitor as they are quite fragile and the source of that rpm signal your diagram shows... That pin is only a 1V supply to your Tacho (via the ignitor) so seeing a 12V spike (just with the ground disconnected, the ECU may have hunted for a ground via the Tacho, maybe).

[Philip Lee]

I would hazard a guess that maybe (depending on where the cuts to your harness where made) there has been a wire either crossed or the ground is somehow not enough of a short circuit now.

A vacuum leak (to answer your earlier post) can be any vacuum hose loose or unplugged causing erratic idle.

I hope you didn't fry your ignitor as they are quite fragile and the source of that rpm signal your diagram shows... That pin is only a 1V supply to your Tacho (via the ignitor) so seeing a 12V spike (just with the ground disconnected, the ECU may have hunted for a ground via the Tacho, maybe).

thanks ampz.

i'd think the most likely cause would be a wire is shorted and fired up something which i dunno.

i doubt it's vacuum leak cos it's not just idle. it's blowing black smoke big time after 2000rpm.

we pulled out the plug and all 4 of them are black. not sure if it's caused by normal use or by the current problem.

[bruce]

Howabout disconnecting the battery overnight? (Not sure if that's any better than 90 mins though???)

[Philip Lee]

Howabout disconnecting the battery overnight? (Not sure if that's any better than 90 mins though???)

thanks bruce.

that was done on Saturday night/Sunday morning. a mechanic is looking at the car now.

[Philip Lee]

carsokay,

thanks for your tip.

i know what you mean about the fine-wire braid. i dun think those touch the signal wire. but i'll check it again to make sure.

thanks
Philip

[Philip Lee]

latest update:

the mechanic checked the ECU and it's reporting a fault with AFM.

we have since tried 5 other ones and still the same problem......

might now check what carsokay offered.